(a) Field of the Invention
The present invention relates to a mask for fabricating a liquid crystal display, and a method of exposing a substrate for a liquid crystal display to light using the mask.
(b) Description of the Related Art
Generally, a liquid crystal display has two substrates with electrodes, and a liquid crystal layer sandwiched between the two substrates. Voltages are applied to the electrodes so that the liquid crystal molecules in the liquid crystal layer are re-oriented to thereby control the light transmission. The electrodes may be all formed at one of the substrates.
In order to form various kinds of patterns at the substrate, photolithography is made with respect to the substrate while involving the step of light exposing.
Conventionally, a stepper or an aligner is used for the light exposing purpose.
In the case of use of the stepper, a mini-sized mask is introduced. The substrate is partitioned into several shot regions, and exposed to light while moving the stepper mask over the substrate in voluntary directions. The stepper mask and the substrate are mounted at the stepper such that they are aligned with each other in an appropriate manner.
In the case of use of the aligner, a large-sized mask is introduced such that the entire area of the substrate is exposed to light only with one shot. The aligner mask is first mounted at the aligner, and the substrate is then aligned with the aligner mask. The aligner is preferably used in fabricating the liquid crystal display.
However, the use of the aligner involves the following problem. As the size of the substrate becomes enlarged to be larger than the existent aligner, it cannot be exposed to light through one mask with one shot. Accordingly, stitch failure is liable to be made at the resulting display device. Therefore, it is required that a new typed light exposing device or design technique should be developed. For instance, such a technique may be made with respect to the inter-shot alignment in the process of exposing the large-sized substrate to light.
It is an object of the present invention to provide a mask for fabricating a liquid crystal display which makes the correct inter-shot alignment with the large-sized substrate while preventing the stitch failure.
This and other objects may be achieved by a mask with different mask patterns for making shots in a separate manner. A large-sized substrate is exposed to light using such a mask.
Specifically, the mask for fabricating a liquid crystal display with a substrate includes a first mask pattern placed at the center of the substrate with the center line to expose the center of the substrate to light. A second mask pattern is placed to the left of the first mask pattern to expose the left side of the substrate to light. The second mask pattern is spaced apart from the first mask pattern with a first distance. A third mask pattern is placed to the right of the first mask pattern to expose the right side of the substrate to light. The third mask pattern is spaced apart from the first mask pattern with a second distance.
Alignment keys for the light exposing are formed at the first mask pattern. The alignment keys are formed with a pair of first alignment patterns placed to the left and to the right of the center line of the mask symmetrical to each other with respect to the center line of the mask, a pair of second alignment patterns placed to the right of the first alignment patterns while being spaced apart from the first alignment patterns with the first distance, and a pair of third alignment patterns placed to the left of the first alignment patterns while being spaced apart from the first alignment patterns with the second distance.
In a method of exposing a substrate for a liquid crystal display to light, a substrate partitioned with a center portion, a left portion and a right portion is first prepared. A mask with first to third mask patterns is also prepared. The first mask pattern is-placed at the center of the substrate with the center line to expose the center portion of the substrate to light. The second mask pattern is placed to the left of the first mask pattern to expose the left side of the substrate to light while being spaced apart from the left side of the first mask pattern with a first distance. The third mask pattern is placed to the right of the first mask pattern to expose the right side of the substrate to light while being spaced apart from the right side of the first mask pattern with a second distance. The mask and the substrate are then aligned with each other. Thereafter, the light exposing with respect to the center portion, the left portion and the right portion of the substrate are made using the mask in a separate manner.
First alignment keys are formed at the first mask pattern of the mask, and second alignment keys are formed at the center portion of the substrate such that the second alignment keys match to the first alignment keys. The first alignment keys are formed with a pair of first alignment patterns placed to the left and to the right of the center line of the mask symmetrical to each other with respect to the center line of the mask, a pair of second alignment patterns placed to the right of the first alignment patterns while being spaced apart from the first alignment patterns with the first distance, and a pair of third alignment patterns placed to the left of the first alignment patterns while being spaced apart from the first alignment patterns with the second distance.
The alignment of the mask with the substrate is made through combining the first alignment keys of the first mask pattern with the second alignment keys of the substrate, and the light exposing with respect to the center portion of the substrate is made using the first mask pattern. At this time, the light exposing with respect to the substrate using the mask is made while intercepting the mask and the substrate with a light interception member of a light exposing device except for the first mask pattern.
The alignment of the mask with the substrate is made through combining the first alignment patterns of the first mask pattern with the second alignment patterns of the substrate, and the light exposing with respect to the left portion of the substrate is made using the second mask pattern. At this time, the light exposing with respect to the substrate using the mask is made while intercepting the mask and the substrate with a light interception member of a light exposing device except for the second mask pattern.
The alignment of the mask with the substrate is made through combining the first alignment patterns of the first mask pattern with the third alignment patterns of the substrate, and the light exposing with respect to the right portion of the substrate is made using the third mask pattern. At this time, the light exposing with respect to the substrate using the mask is made while intercepting the mask and the substrate with a light interception member of a light exposing device except for the third mask pattern.